Comedy, explained Aristotle, has a vague history, because at first no one took it seriously. We cannot know for certain if Aristotle was deadpanning, but his observation would amuse Saul Austerlitz. According to Austerlitz, American film comedy has not been taken seriously, either. In fact, the author quips, it is American film’s “bastard stepchild.” With his latest book “Another Fine Mess: A History of American Film Comedy,” Austerlitz gives us a broad survey of the genre, hoping to spark debate.